Effect of Stress and Galvanic Factors on the Corrosion Behave of Aluminum Alloy

The interaction between stress and galvanic during the corrosion process of 5050 aluminum alloys was studied and the evolution of mechanics properties was indicated. Electrochemical impedance technique and scanning electron microscopy were used to analyze the surface electrochemical states and the corrosion morphology. At the same time, corrosion kinetics and thermodynamic theory were used to analyze the influencing mechanism of the stress factor and the galvanic factor. The results show that both of galvanic factor and tensile stress factor can increase the corrosion potential of aluminum alloys and result in the corrosion resistance decrease. With decreasing corrosion resistance, the mechanical properties of aluminum alloys decrease. These phenomena are attributed to two reasons： One is that aluminum alloys may under the condition of anodic polarization after coupled with 40 Cr Ni Mo A steel, so the corrosion can be promoted; The other is that with increasing stress, the electrochemical potential of 5050 aluminum alloys decreases and the potential difference between two materials increases, so the corrosion becomes serious. Compared to the stress factor, the galvanic factor is significant.

Galvanic Corrosion of Magnesium Alloy and Aluminum Alloy by Kelvin Probe

Galvanic corrosion on samples of AZ91D magnesium alloy coupled with 2A12 aluminum alloy during neutral salt spray test was investigated.The variations of the surface potential were measured using scanning kelvin probe（SKP）.The results showed that galvanic effect on the corrosion of AZ91D magnesium alloy is closely related to the potential difference between the anodic and cathodic materials.In the initial period,corrosion only occurred in a narrow area at the coupling interface because of the limited distance galvanic current.Then,the corrosion rate of 2A12 aluminum alloy was accelerated due to its poor stability in strong alkali environment,which was attributed to the strong alkalization caused by the corrosion of AZ91D magnesium alloy.With the increase of the potential of 2A12 aluminum alloy as a result of the continuous covering of corrosion products,the potential difference between the two materials was enlarged,which enhanced the galvanic corrosion.

Quick selection of aluminum galvanic anodes in oil brine via galvanic current

According to dynamics of coupled galvanic anode with carbon steel,the integral of galvanic current vs.time is approximately equal to actual current capacity of galvanic anode.Galvanic current of cast aluminum galvanic anode coupled with carbon steel is tested in3.5%NaCl solution and ambient temperature.Rapid evaluation the performance of galvanic anode using galvanic current is feasible,and the test time is20min.The galvanic current is used to select aluminum galvanic anodes in oil brine,and then test the galvanic anodes with impressed current test method.The result shows,the performance of galvanic anodes degrads in oil brine,but has not much difference in the two media to the preferable anodes,and the optimal galvanic anode is gained.